Cells – 1
That Living organisms are composed of one or more cells is one of the unifying
principles of biology.
A cell is a unique compartment, composed of molecules
organized into a structural and functional unit and separated from the external
environment by a membrane boundary.
The cell is the smallest unit of life.
oldest cellular fossils date back 3.5 billion years and oxygen-producing
cyanobacteria are found in 2.5 billion year old stromatolite fossils in Australia
(where living stromatolites are found, too).
Living and Fossil Cyanobacteria
Fossil and Living Stromatolites
For single-celled organisms, all requirements for life: growth, development,
regulation, reproduction and interactions with their environment are met within a
Multicellular plants, fungi and animals are comprised of collections of
cells and tissues, each with specialized structures and functions that contribute to
These two statements: (Living organisms are composed of cells and cells are the
structural and functional unit of life) along with a third:
all cells come from pre-
existing cells, form the cell theory.
In this chapter, we will see how the structure
of cells and, in particular, the structure of cell components, facilitates the
functioning of cells.
Learning about cell structure and function is challenging.
Cells, for the most part,
Moreover, when we turn to the functioning of cells, and their
component parts, the organelles, we often affect the very structure we are hoping
to learn about with our manipulations.
Until the first light microscopes 400+ years ago, no one had really seen cells.
However, even the best light microscope can not clearly resolve images magnified
more than 1000x times (for detail about 0.2
There are a variety of methods
used to enhance the quality of images viewed with a light microscope, which, in
combination, can help researchers.
Some examples are illustrated in your text.
Many cell components that we discuss today were not known or seen prior to the
use of electron microscopes.
Electron microscopes can resolve images of about 2
The scanning-tunneling microscope can generate computer surface images of
single atoms magnified about 2 million times.
Bellevue College is fortunate to have
a scanning electron microscope donated for student (and faculty) use by a local